Semiconductor device with protection circuit protecting internal circuit from static electricity

ABSTRACT

A protection circuit described herein protects an LCD module from static electricity generated at a first positive power supply terminal in a process of manufacturing the LCD module. The protection circuit includes four diodes connected in series between a first node connected to the first positive power supply terminal and a second node receiving a reference potential, and a diode connected between the second and first nodes. When a first positive power supply voltage (10V) is applied to the first positive power supply terminal, the four diodes do not conduct. Therefore, a current consumption of the LCD module can accurately be measured.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a semiconductor device. Moreparticularly, the present invention relates to a semiconductor devicewith a protection circuit protecting an internal circuit from staticelectricity generated at an input terminal.

2. Description of the Background Art

A conventional TFT (thin film transistor) of an active matrix typeliquid crystal panel has been made of amorphous silicon. Recently,however, formation of a TFT from polysilicon has been underconsideration. Conventionally, a scan line drive circuit or a data linedrive circuit or the like has been configured of an LSI made ofcrystalline silicon and provided separately from a liquid crystal panelmade of amorphous silicon. Since a mobility of polysilicon isapproximately 100 times higher than that of amorphous silicon, however,a liquid crystal panel, a scan line drive circuit, a data line drivecircuit or the like can be made of polysilicon to obtain one LCD (liquidcrystal display) module.

A polysilicon TFT, however, exhibits a wide variation in TFTcharacteristics such as a threshold voltage or a mobility. Thus, a widevariation in a current consumption of the LCD module results. Therefore,it is of the utmost importance to accurately inspect whether or not thecurrent consumption of the LCD module satisfies the standard value.

In a conventional array inspection, after charging a capacitor providedcorresponding to each liquid crystal cell, a discharge current isdetected. Based on a result of the detection, an inspection is performedas to whether or not the array is normal. The inspection time, however,can significantly be reduced, if the current consumption of the LCDmodule is inspected prior to this array inspection so that theconventional array inspection can be omitted when the inspection of thecurrent consumption detects an unsatisfactory value. In this sense aswell, an accurate detection of the current consumption of the LCD moduleis important.

Furthermore, a gate oxide film of the polysilicon TFT is thinner thanthat of an amorphous silicon TFT. Accordingly, the gate oxide film ofthe polysilicon TFT is more susceptible to damage from staticelectricity. As a method of preventing damage to the TFT from staticelectricity in an array manufacturing process, a method ofshort-circuiting terminals has been provided.

As a method of applying a voltage to a terminal in an array inspectionas well as preventing damage to a TFT from static electricity, thefollowing have been provided, i.e., a method of connecting a resistanceelement between each terminal and a conductor pattern, and a method ofconnecting two diodes in opposite directions in parallel between eachterminal and a conductor pattern (see, for example, Japanese PatentLaying-Open No. 11-119257).

In order to accurately measure the current consumption of the LCDmodule, a resistance value of a resistance element or a diode needs tobe high. The high resistance value of the resistance element or thediode, however, makes it difficult to flow static electricity out. Thisresults in the LCD module having a low resistance to static electricity.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor devicethe current consumption of which can accurately be measured and which ishighly resistant to static electricity.

A semiconductor device in accordance with the present invention includesa first input terminal receiving a first positive voltage externally inan inspection of the semiconductor device and a normal operation of thesemiconductor device, an internal circuit connected to the first inputterminal and performing a prescribed operation, and a first protectioncircuit protecting the internal circuit from static electricitygenerated at the first input terminal. The first protection circuitincludes a plurality of first diode elements connected in series betweenthe first input terminal and a line of a reference potential andconducting in response to a voltage of the first input terminalexceeding a second positive voltage higher than the first positivevoltage, and a second diode element connected between the line of thereference potential and the first input terminal. Accordingly, when thefirst positive voltage is applied to the first input terminal in theinspection, the plurality of first diode elements do not conduct.Therefore, a current consumption of the semiconductor device canaccurately be measured. Furthermore, when the voltage of the first inputterminal exceeds the second positive voltage higher than the firstpositive voltage, the plurality of first diode elements conduct. As aresult, a reliable protection of the internal circuit from the staticelectricity can be ensured.

Another semiconductor device in accordance with the present inventionincludes an input terminal receiving a first negative voltage externallyin an inspection of the semiconductor device and a normal operation ofthe semiconductor device, an internal circuit connected to the inputterminal and performing a prescribed operation, and a protection circuitprotecting the internal circuit from static electricity generated at theinput terminal. The protection circuit includes a plurality of firstdiode elements connected in series between a line of a referencepotential and the input terminal and conducting in response to a voltageof the input terminal going lower than a second negative voltage lowerthan the first negative voltage, and a second diode element connectedbetween the input terminal and the line of the reference potential.Accordingly, when the first negative voltage is applied to the inputterminal in the inspection, the plurality of first diode elements do notconduct. Therefore, a current consumption of the semiconductor devicecan accurately be measured. In addition, when the voltage of the inputterminal exceeds the second negative voltage lower than the firstnegative voltage, the plurality of first diode elements conduct. As aresult, a reliable protection of the internal circuit from the staticelectricity can be ensured.

A further semiconductor device in accordance with the present inventionincludes an input terminal receiving externally a voltage of at most afirst positive voltage and at least a first negative voltage in aninspection of the semiconductor device and a normal operation of thesemiconductor device, an internal circuit connected to the inputterminal and performing a prescribed operation, and a protection circuitprotecting the internal circuit from static electricity generated at theinput terminal. The protection circuit includes a plurality of firstdiode elements connected in series between the input terminal and a lineof a reference potential line and conducting in response to a voltage ofthe input terminal exceeding a second positive voltage higher than thefirst positive voltage, and a plurality of second diode elementsconnected in series between the line of the reference potential and theinput terminal and conducting in response to the voltage of the inputterminal going lower than a second negative voltage lower than the firstnegative voltage. Accordingly, when the voltage of at most the firstpositive voltage and at least the first negative voltage is applied tothe input terminal in the inspection, the plurality of first diodeelements and the plurality of second diode elements do not conduct.Therefore, a current consumption of the semiconductor device canaccurately be measured. In addition, when the voltage of the inputterminal exceeds the second positive voltage higher than the firstpositive voltage and when the voltage of the input terminal exceeds thesecond negative voltage lower than the first negative voltage, theplurality of first diode elements and the plurality of second diodeelements conduct, respectively. As a result, a reliable protection ofthe internal circuit from static electricity can be ensured.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an overall configuration of a colorliquid crystal display device in accordance with one embodiment of thepresent invention.

FIG. 2 is a circuit diagram showing a configuration of a liquid crystaldrive circuit provided corresponding to each liquid crystal cell shownin FIG. 1.

FIG. 3 is a circuit block diagram for describing a method of inspectingthe color liquid crystal display device shown in FIG. 1.

FIGS. 4A–4C are circuit diagrams showing a configuration of a protectioncircuit 30 in FIG. 3.

FIGS. 5A–5C are circuit diagrams showing a configuration of a protectioncircuit 31 in FIG. 3.

FIGS. 6A–6C are circuit diagrams showing a configuration of a protectioncircuit 36 in FIG. 3.

FIG. 7 is a circuit block diagram showing an exemplary modification ofthe present embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram showing a configuration of a color liquidcrystal display device in accordance with one embodiment of the presentinvention. In FIG. 1, the color liquid crystal display device includes apixel array portion 1, a vertical scanning circuit 7, and a horizontalscanning circuit 8, and is provided for a mobile phone, for example.

Pixel array portion 1 includes a plurality of liquid crystal cells 2arranged in a plurality of rows and columns, a plurality of scan lines 4respectively provided corresponding to the plurality of rows, aplurality of common potential lines 5 respectively providedcorresponding to the plurality of rows, and a plurality of data lines 6respectively provided corresponding to the plurality of columns. Theplurality of common potential lines 5 are connected to each other.

Liquid crystal cells 2 are previously grouped together in threes at eachrow. Three liquid crystal cells 2 in each group are provided with colorfilters of R, G, and B, respectively. Three liquid crystal cells 2 ineach group constitute one pixel 3.

As shown in FIG. 2, each liquid crystal cell 2 is provided with a liquidcrystal drive circuit 10. Liquid crystal drive circuit 10 includes an Ntype TFT 11 and a capacitor 12. N type TFT 11 is connected between dataline 6 and one electrode 2 a of liquid crystal cell 2. N type TFT 11 hasits gate connected to scan line 4. Capacitor 12 is connected between oneelectrode 2 a of liquid crystal cell 2 and common potential line 5. Acommon potential VCOM is applied to common potential line 5. The otherelectrode of liquid crystal cell 2 is connected to an oppositeelectrode. A potential same as common potential VCOM is generallyapplied to the opposite electrode.

Referring back to FIG. 1, vertical scanning circuit 7 operates inresponse to an image signal to select the plurality of scan lines 4sequentially, each for a prescribed period of time, and set the selectedscan line 4 to an H level of a selected level. When scan line 4 israised to the H level of the selected level, N type TFT 11 in FIG. 2conducts. Then, one electrode 2 a of each liquid crystal cell 2corresponding to that scan line 4 and data line 6 corresponding to thatliquid crystal cell 2 are coupled.

While one scan line 4 is selected by vertical scanning circuit 7 inaccordance with the image signal, horizontal scanning circuit 8 appliesa graduation potential VG to each data line 6 and also applies commonpotential VCOM to common potential line 5. A light transmittance ofliquid crystal cell 2 varies depending on a voltage between theelectrodes.

When all the liquid crystal cells 2 in pixel array portion 1 are scannedby vertical scanning circuit 7 and horizontal scanning circuit 8, onecolor image is displayed at pixel array portion 1.

FIG. 3 is a circuit block diagram for describing a method of inspectingthe color liquid crystal display device shown in FIGS. 1 and 2. In FIG.3, in this inspection method, an LCD module 15 that is a color liquidcrystal display device assembly, a plurality of protection circuits 30to 38, and a reference potential line 40 are provided at a surface of aglass substrate (not shown).

LCD module 15 includes a TFT array 1 a, a scan line drive circuit 16, adata line drive circuit 17, a first positive power supply terminal 20, afirst negative power supply terminal 21, a first start terminal 22, afirst clock terminal 23, a second start terminal 24, a second clockterminal 25, a plurality of data terminals 26, a second positive powersupply terminal 27, and a second negative power supply terminal 28provided within a region of the quadrangular module.

TFT array 1 a includes the plurality of scan lines 4, the plurality ofdata lines 6, a plurality of N type TFTs 11, a plurality of capacitors12, and one electrodes of liquid crystal cells 2 formed on the glasssubstrate. At each crossing point of scan line 4 and data line 6, a setof N type TFT 11, capacitor 12, and one electrode of liquid crystal cell2 are provided. A liquid crystal panel is produced by introducing liquidcrystal between the TFT array substrate and another glass substrate.Another glass substrate is provided with an electrode opposite to oneelectrode of liquid crystal cell 2 and a color filter.

Scan line drive circuit 16 is a part of vertical scanning circuit 7.Scan line drive circuit 16 is driven by a first positive power supplyvoltage VP1 and a first negative power supply voltage VN1 appliedthrough terminals 20 and 21. Scan line drive circuit 16 operates insynchronization with a first start signal ST1 and a first clock signalCLK1 applied through terminals 22 and 23. Scan line drive circuit 16sequentially selects the plurality of scan lines 4 and raises theselected scan line to the H level of the selected level.

Data line drive circuit 17 is a part of horizontal scanning circuit 8.Data line drive circuit 17 is driven by a second positive power supplyvoltage VP2 and a second negative power supply voltage VN2 appliedthrough terminals 27 and 28. Data line drive circuit 17 operates insynchronization with a second start signal ST2 and a second clock signalCLK2 applied through terminals 24 and 25. While one scan line 4 isselected, data line drive circuit 17 writes a plurality of graduationpotentials VGs applied through the plurality of data terminals 26 to aplurality of liquid crystal cells 2 corresponding to the selected scanline 4.

Terminals 20 to 25, 27, 28, and the plurality of data terminals 26 areprovided along one side of the quadrangular module region and arrangedwith a prescribed pitch therebetween. Each of terminals 20 to 28 is, inan inspection, connected to an inspection device via a probe. After theinspection, each of terminals 20 to 28 is connected to an FPC (flexibleprinted circuit board).

The plurality of protection circuits 30 to 38 are provided externally tothe module region. The plurality of protection circuits 30 to 38 areprovided respectively corresponding to terminals 20 to 28. Each ofprotection circuits 30 to 38 is connected between a correspondingterminal and reference potential line 40. Each of protection circuits 30to 38 flows static electricity generated at the corresponding terminalto reference potential line 40 to protect LCD module 15. Referencepotential line 40 is connected to a terminal for a reference potential(e.g. a ground potential GND terminal). A reference potential VR (e.g. aground potential GND) is applied to reference potential line 40.

FIG. 4A is a circuit diagram showing a configuration of protectioncircuit 30. In FIG. 4A, protection circuit 30 includes four diodes 41connected in series between nodes N41 and N42, and a diode 42 connectedbetween nodes N42 and N41. Node N41 is connected to first positive powersupply terminal 20. Node N42 is connected to reference potential line40.

Diodes 41 and 42 may be N type TFTs 43 and 44 as shown in FIG. 4B, ormay be P type TFTs 45 and 46 as shown in FIG. 4C. A TFT having its gateand drain connected together forms a diode. A threshold voltage Vth ofeach of diodes 41 and 42 is set at 3V.

To check a current in an array inspection, first power supply voltageVP1, i.e. 10V, is applied to first positive power supply terminal 20. Atthis time, diodes 41 and 42 are kept non-conductive. Therefore, acurrent flowing from first positive power supply terminal 20 to LCDmodule 15 can accurately be measured. When positive static electricityis generated at terminal 20 and a voltage of terminal 20 reaches atleast 12V, four diodes 41 conduct. Then, the positive static electricityflows to reference potential line 40. Furthermore, when negative staticelectricity is generated at terminal 20 and the voltage of terminal 20reaches at most 3V, diode 42 conducts. Then, the negative staticelectricity is erased by a current from reference potential line 40.Therefore, damage to LCD module 15 from the static electricity can beprevented. Protection circuits 32 to 35, and 37 are the same inconfiguration as protection circuit 30. In checking a current, 10V or 0Vis applied to each of terminals 32 to 35, and 37.

FIG. 5A is a circuit diagram showing a configuration of protectioncircuit 31. In FIG. 5A, protection circuit 31 includes a diode 51connected between nodes N51 and N52, and two diodes 52 connected inseries between nodes N52 and N51. Node N51 is connected to firstnegative power supply terminal 21. Node N52 is connected to referencepotential line 40.

Diodes 51 and 52 may be N type TFTs 53 and 54 as shown in FIG. 5B, ormay be P type TFTs 55 and 56 as shown in FIG. 5C. A TFT having its gateand drain connected together forms a diode. Threshold voltage Vth ofeach of diodes 51 and 52 is set at 3V.

To check a current in the array inspection, first negative power supplyvoltage VN1, i.e. −5V, is applied to first negative power supplyterminal 21. At this time, diodes 51 and 52 are kept non-conductive.Therefore, a current flowing from first negative power supply terminal21 to LCD module 15 can accurately be measured. When negative staticelectricity is generated at terminal 21 and a voltage of terminal 21reaches at most −5V, two diodes 52 conduct. Then, the negative staticelectricity is erased by a current from reference potential line 40.Furthermore, when positive static electricity is generated at terminal21 and the voltage of terminal 21 reaches at least 3V, diode 51conducts. Then, the positive static electricity flows to referencepotential line 40. Therefore, damage to LCD module 15 from the staticelectricity can be prevented. Protection circuit 38 is the same inconfiguration as protection circuit 31. In checking a current, −5V isapplied to terminal 28 as well.

FIG. 6A is a circuit diagram showing a configuration of protectioncircuit 36. In FIG. 6A, protection circuit 36 includes four diodes 61connected in series between nodes N61 and N62, and two diodes 62connected between nodes N62 and N61. Node N61 is connected to dataterminal 26. Node N62 is connected to reference potential line 40.

Diodes 61 and 62 may be N type TFTs 63 and 64 as shown in FIG. 6B, ormay be P type TFTs 65 and 66 as shown in FIG. 6C. A TFT having its gateand drain connected together forms a diode. Threshold voltage Vth ofeach of diodes 61 and 62 is set at 3V.

To check a current in the array inspection, an upper limit of graduationpotential VG, i.e. 10V, and a lower limit of graduation potential VG,i.e. −5V, are applied to data terminal 26. At this time, diodes 61 and62 are kept non-conductive. Therefore, a current flowing from dataterminal 26 to LCD module 15 can accurately be measured. When positivestatic electricity is generated at terminal 26 and a voltage of terminal26 reaches at least 12V, four diodes 61 conduct. Then, the positivestatic electricity flows to reference potential line 40. Furthermore,when negative static electricity is generated at terminal 26 and thevoltage of terminal 26 reaches at most 6V, two diodes 62 conduct. Then,the negative static electricity is erased by a current from referencepotential line 40. Therefore, damage to LCD module 15 from the staticelectricity can be prevented.

Referring back to FIG. 3, after the inspection is completed, LCD module15 and a corresponding glass substrate portion are removed from theglass substrate. At this time, terminals 20 to 28 are separated fromprotection circuits 30 to 38. Thereafter, another glass substrate isplaced on a surface of TFT array 1 a with liquid crystal interposed toform pixel array portion 1. Furthermore, terminals 20 to 28 areconnected to FPC. The color liquid crystal display device is completed.

FIG. 7 is a circuit block diagram showing a modification of the presentembodiment. Referring to FIG. 7, in this modification, a test circuit70, a second start terminal 71, a second clock terminal 72, a pluralityof data terminals 73, a second power supply terminal 74, a secondnegative power supply terminal 75, a plurality of protection circuits 81to 85, and a reference potential line 90 are further provided outside ofa module region of a glass substrate surface.

In the array inspection, test circuit 70 is driven by second positivepower supply voltage VP2 and second negative power supply voltage VN2applied through terminals 74 and 75. Test circuit 70 operates insynchronization with second start signal ST2 and second clock signalCLK2 applied through terminals 71 and 72. Test circuit 70 appliesgraduation potentials VGs applied through the plurality of dataterminals 73 to a plurality of capacitors 12 corresponding to a selectedscan line 4 to charge each capacitor 12. Then, test circuit 70 detects adischarge current of capacitor 12 and determines from the detectionwhether or not each capacitor 12 is normal.

The plurality of protection circuits 81 to 85 are provided respectivelycorresponding to terminals 71 to 75. Each of protection circuits 81 to85 is connected between a corresponding terminal and reference potentialline 90. Each of protection circuits 81 to 85 flows static electricitygenerated at the corresponding terminal to reference potential line 90to protect test circuit 70 and LCD module 15. Reference potential line90 is connected to a terminal for a reference potential (e.g. a groundpotential GND terminal). Reference potential VR (e.g. ground potentialGND) is applied to reference potential line 90. Protection circuits 81to 85 are the same in configuration as protection circuits 34 to 38,respectively. Therefore, a current consumption of test circuit 70 canaccurately be detected.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

1. A semiconductor device comprising: a first input terminal receiving afirst positive voltage externally in an inspection of said semiconductordevice and a normal operation of said semiconductor device; an internalcircuit connected to said first input terminal and performing aprescribed operation; at least a portion of said internal circuit isformed with a thin film transistor; and a first protection circuitprotecting said internal circuit from static electricity generated atsaid first input terminal, said first protection circuit including aplurality of first diode elements connected in series between said firstinput terminal and a line of a reference potential and conducting inresponse to a voltage of said first input terminal exceeding a secondpositive voltage higher than said first positive voltage, and a seconddiode element connected between the line of said reference potential andsaid first input terminal and conducting in response to the voltage ofsaid first input terminal going lower than a first negative voltage;wherein each of said plurality of first diode elements and said seconddiode element is formed with a thin film transistor having its gate anddrain connected together.
 2. The semiconductor device according to claim1, further comprising: a second input terminal connected to saidinternal circuit and receiving a second negative voltage externally inthe inspection of said semiconductor device and the normal operation ofsaid semiconductor device; and a second protection circuit protectingsaid internal circuit from static electricity generated at said secondinput terminal; wherein said second protection circuit includes aplurality of third diode elements connected in series between the lineof said reference potential and said second input terminal andconducting in response to a voltage of said second input terminal goinglower than a third negative voltage lower than said second negativevoltage, and a fourth diode element connected between said second inputterminal and the line of said reference potential and conducting inresponse to the voltage of said second input terminal exceeding a thirdpositive voltage; and each of said plurality of third diode elements andsaid fourth diode element is formed with a thin film transistor havingits gate and drain connected together.
 3. The semiconductor deviceaccording to claim 2, further comprising: a third input terminalconnected to said internal circuit and receiving externally a voltage ofat most a fourth positive voltage and at least a fourth negative voltagein the inspection of said semiconductor device and the normal operationof said semiconductor device; and a third protection circuit protectingsaid internal circuit from static electricity generated at said thirdinput terminal; wherein said third protection circuit includes aplurality of fifth diode elements connected in series between said thirdinput terminal and the line of said reference potential and conductingin response to the voltage of said first input terminal exceeding afifth positive voltage higher than said fourth positive voltage, and aplurality of sixth diode elements connected in series between the lineof said reference potential and said third input terminal and conductingin response to a voltage of said third input terminal going lower than afifth negative voltage lower than said fourth negative voltage; and eachof said plurality of fifth diode elements and said plurality of sixthdiode elements is formed with a thin film transistor having its gate anddrain connected together.
 4. A semiconductor device comprising: an inputterminal receiving a first negative voltage externally in an inspectionof said semiconductor device and a normal operation of saidsemiconductor device; an internal circuit connected to said inputterminal and performing a prescribed operation, at least a portion ofsaid internal circuit is formed with a thin film transistor; and aprotection circuit protecting said internal circuit from staticelectricity generated at said input terminal, said protection circuitincluding a plurality of first diode elements connected in seriesbetween a line of a reference potential and said input terminal andconducting in response to a voltage of said input terminal going lowerthan a second negative voltage lower than said first negative voltage,and a second diode element connected between said input terminal and theline of said reference potential and conducting in response to thevoltage of said input terminal exceeding a predetermined positivevoltage; wherein each of said plurality of first diode elements and saidsecond diode element is formed with a thin film transistor having itsgate and drain connected together.
 5. A semiconductor device comprising:an input terminal receiving externally a voltage of at most a firstpositive voltage and at least a first negative voltage in an inspectionof said semiconductor device and a normal operation of saidsemiconductor device; an internal circuit connected to said inputterminal and performing a prescribed operation, at least a portion ofsaid internal circuit is formed with a thin film transistor; and aprotection circuit protecting said internal circuit from staticelectricity generated at said input terminal, said protection circuitincluding a plurality of first diode elements connected in seriesbetween said input terminal and a line of a reference potential andconducting in response to a voltage of said input terminal exceeding asecond positive voltage higher than said first positive voltage, and aplurality of second diode elements connected in series between the lineof said reference potential and said input terminal and conducting inresponse to the voltage of said input terminal going lower than a secondnegative voltage lower than said first negative voltage; wherein each ofsaid plurality of first diode elements and said plurality of seconddiode elements is formed with a thin film transistor having its gate anddrain connected together.
 6. A semiconductor device comprising: a firstinput terminal receiving a first positive voltage externally in aninspection of said semiconductor device and a normal operation of saidsemiconductor device; an internal circuit connected to said first inputterminal and performing a prescribed operation; a first protectioncircuit protecting said internal circuit from static electricitygenerated at said first input terminal, said first protection circuitincluding a plurality of first diode elements connected in seriesbetween said first input terminal and a line of a reference potentialand conducting in response to a voltage of said first input terminalexceeding a second positive voltage higher than said first positivevoltage, and a second diode element connected between the line of saidreference potential and said first input terminal and conducting inresponse to the voltage of said first input terminal going lower than afirst negative voltage; a second input terminal connected said internalcircuit and receiving a second negative voltage externally in theinspection of said semiconductor device and the normal operation of saidsemiconductor device; a second protection circuit protecting saidinternal circuit from static electricity generated at said second inputterminal, said second protection circuit including a plurality of thirddiode elements connected in series between the line of said referencepotential and said second input terminal and conducting in response to avoltage of said second input terminal going lower than a third negativevoltage lower than said second negative voltage, and a fourth diodeelement connected between said second input terminal and the line ofsaid reference potential and conducting in response to the voltage ofsaid second input terminal exceeding a third positive voltage; a thirdinput terminal connected to said internal circuit and receivingexternally a voltage of at most a fourth positive voltage and at least afourth negative voltage in the inspection of said semiconductor deviceand the normal operation of said semiconductor device; and a thirdprotection circuit protecting said internal circuit from staticelectricity generated at said third input terminal, said thirdprotection circuit including a plurality of fifth diode elementsconnected in series between said third input terminal and the line ofsaid reference potential and conducting in response to the voltage ofsaid first input terminal exceeding a fifth positive voltage higher thansaid fourth positive voltage, and a plurality of sixth diode elementsconnected in series between the line of said reference potential andsaid third input terminal and conducting in response to a voltage ofsaid third input terminal going lower than a fifth negative voltagelower than said fourth negative voltage.
 7. The semiconductor deviceaccording to claim 1, wherein said semiconductor device is formed on onesubstrate, and a portion of the substrate having said first protectioncircuit formed thereon is isolated from a portion of the substratehaving said first input terminal and said internal circuit formedthereon after the inspection of said semiconductor device.
 8. Thesemiconductor device according to claim 7, wherein said semiconductordevice forms a portion of a liquid crystal display device, and saidinternal circuit includes a thin film transistor array, a scan linedrive circuit and a data line drive circuit.